It is well known to provide a seat belt retractor in which a reel is locked against belt unwinding rotation by a pawl which is pivoted to engage with ratchet teeth provided on the reel.
It is also known to provide mechanism for moving the pawl to the ratchet teeth engaging position in response to a sensed velocity or acceleration of belt unwinding reel rotation. Such a retractor typically has a clutch member which is rotatably mounted on the end of the reel shaft and has an arm which is engageable with the pawl. The clutch member remains stationary during normal winding and unwinding of the belt so that the pawl remains disengaged from the ratchet teeth. A clutch pawl is carried on the end of the reel shaft normally disengaged from the clutch member but is movable into engagement with ratchet teeth on the clutch member by centrifugal forces acting on the clutch pawl or by the lagging rotation of an inertia wheel rotatably mounted on the reel.
It is also well known to provide a tension reliever for locking a belt reel against belt winding rotation so that the belt is held in a tension free slackened length about the occupant. Such tension relief mechanisms typically comprise an auxiliary ratchet plate carried by the wheel and a pawl which is moved to engage the ratchet teeth so that the reel is held against belt winding rotation.